1. Field of the Invention
This invention relates generally to the field of fault detection systems for automotive vehicle alternator battery electrical energy circuits which operate to continuously monitor the performance of the circuit when in use.
2. Description of the Prior Art
Voltage regulator controlled automotive battery charging systems are commonly used to keep an automotive storage battery at full charge level and to provide sufficient electrical power for the operation of the various automobile electrical accessories. Normally an alternator is driven by means of a belt-and-pulley arrangement coupled to the internal combustion engine of the automobile to provide a rectified output current. The alternator operation is controlled by a voltage regulator which senses the battery voltage and controls the field coil excitation for the alternator in response to the sensed voltage. An indicator lamp is typically used in such circuits to provide an indication to the automobile operator of the absence of an alternator output to alert the operator of the automobile to a malfunctioning in the electrical system.
In some prior art systems, the DC current is passed through the indicator lamp prior to commencement of the rotation of the alternator rotor to provide the initial alternator field coil excitation. This is the most common method where the steel-pole pieces in the alternator have been designed to retain little or no residual or permanent magnetism and it is, therefore, necessary to pass electrical energy through the field winding to establish the magnetic flux in the presence of the rotor in order to initiate an electrical output. Typically, such prior art systems provide an indicator light warning to the automobile operator only to indicate an alternator malfunction resulting from a low alternator charging output signal. Examples of such prior art systems may be found in U.S. Pat. No. 3,365,646 and U.S. Pat. No. 3,138,751, both of which are assigned to the same assignee as the present invention.
Other prior art systems have recognized the need for providing a visual indication of other possible faults in the alternator, voltage-regulator and battery system. U.S. Pat. No. 3,673,588 assigned to the same assignee as the present invention is an example of such a system and teaches the use of separate sensing circuits to separately excite different display lamps to indicate either high or low voltage conditions.
Another prior art system provides for detection of some fault conditions in an operating alternator battery system. The occurrence of three symptoms primarly due to alternator malfunction are monitored: high voltage, low voltage and excessive ripple. Three separate detectors operate in parallel to turn on the operator indicator light whenever a fixed signal threshold level has been reached for any of the detectors. This system cannot classify or differentiate among the symptoms nor does it provide any protection for the electrical system upon a detection of a fault.
Additional prior systems show fault indicator devices for testing the operation of an alternator, voltage-regulator, battery system by the attachment of an external test circuit device. As is common with all such test equipment, it is designed not to be permanently attached to the alternator-battery-voltage regulator system but rather coupled selectively only for the purpose of diagnosing a malfunction. Normally some of the features of the battery charging system are disabled while the automobile engine is started and various electrical loads drawn to simulate normal operation of the alternator-battery system. With various conductor attachments such test equipment uses either separate indicator lights or a common indicator light to designate different types of generalized malfunctions in the alternator-battery system. Various automobile manufacturers' test manuals show such test equipment and the selective disabling of portions of an automobile alternator-battery system. There is usually a description of manually attaching various cables at predetermined positions in the electrical circuit to monitor the performance of an individual feature under a simulated load. In all cases, the alternator-battery system has been disabled in some manner and the operation is merely a simulated test for that portion to which the test device has been connected.
In another prior external testing system, the ignition switch is disconnected from the circuit with the engine running and a test device is connected to monitor the alternator output. Disconnection of the ignition switch disables the automotive circuit by removing both the battery and accessory electrical loads. A single fault indicator light is used in a constant on mode to indicate a general type of fault which is characterized by voltage spikes and in a flashing mode to indicate an abnormal voltage output. This system merely detects generalized fault characteristics without distinguishing or identifying the fault.
All of the prior art systems use either a single light to indicate a malfunction or a series of display lights coupled to various separate circuits which are individually connected to identify a malfunction. None of these prior art systems has both the advantage of detecting the occurrence of a fault in an operating alternator, voltage-regulator battery system and diagnosing the fault to determine which of the several major electrical component systems may be undergoing a malfunctioning condition. The present invention is intended to be permanently attached to a functioning alternator, voltage-regulator battery system and, at any given time, to indicate not only the fact that a fault has occurred but to identify the major electrical component such as alternator which is undergoing the malfunction.